Leptospirosis – Causes, Symptoms, Diagnosis and Treatment

Leptospirosis is a zoonotic disease caused by all leptospiras irrespective of their specific serotypes. Leptospira are tightly coiled motile spirochaetcs and are broadly divided into two species – Leptospira Interrogans comprising of all pathogenic strains and Leptospira biflexa which consists of non-pathogenic strains. Of the various serotypes human infection is caused by L. icterohaemorrhagic (from rodents), L. canicola (from dogs and pigs) and L. hardjo (from cattle).

Lepospirosis is of world wide distribution. Infection in humans is incidental. It occurs in a wide range of wild animals, live stock, rodents and dogs. In these animals leptospira persist in the kidney without causing apparent disease and are shed in urine in massive number.

Human infection occurs either by direct contact with urine or tissue of an infected animal or indirectly through contaminated water, soil or vegetation. It can survive in untreated water for months or years. But can not survive heat or salt water. The usual mode of entry in humans is abraded or broken skin especially of the feet and extremities and exposed conjunctival, nasal or oral mucous surfaces.

Pathogenesis

The pathogenesis of leptospirosis is not well understood. The organism is found in the walls of capillaries and large and medium sized vessels and produces vascular injury. Their dissemination and proliferation in various tissues results in ecchymosis and petechiae in them. These hemorrhages are widespread and are prominent in skeletal muscles, kidneys, adrenals, liver, spleen and lungs.

In skeletal muscles there are focal and necrotic changes. Hepatic lesions include mild degenerative changes in hepatocytes hypertrophy and hyperplasia of Kupifer cells, erythrophagocytosis and cholestasis. In addition there is cloudy swelling of parenchymal cells and disruption of liver cords.

Kidneys show diffuse tubulointerstitial inflammation. A pulmonary finding consists of congested lungs with localized hemorrhagic pneumonitis. Similar changes varying from mild to moderate degree may develop in other organs.

Clinical features

The incubation period of the disease is 2 to 26 days (average 10 days).

Leptospirosis presents in two phases

Anicteric leptospirosis (First phase) and immune phase (second phase) separated from the first by an asymptomatic period of 1-3 days. In the first (Leptospiraemic phase) the onset is abrupt with fever, chills, headache myalgia, conjunctival suffusion, Anorexia, nausea and vomiting. The fever is high and remittent. Myalgia is severe and distressing.

Other organs may be involved like kidney, liver and spleen. There may be pain in abdomen as well as neck rigidity. Conjunctival suffusion which appears on the third or fourth day is characteristic. Skin manifestations include macular, maculopapular or urticarial rashes. The first lasts from 3-9 days and terminates with defervescence. There is disappearance of leptospiras from the blood and cerebro spinal fluid.

After symptom period of 1-3 days, the second (immune) of the disease develops. It coincides with the appearance of 1gM antibodies in the serum. Clinically there is fever, meningism (Headache, neck rigidity, photophobia) and aseptic meningitis. CSF shows rise in proteins and lymphocytes. Complications like myelitis, encephalitis, optic neuritis, uveitis iridocyclitis chorioretinitis and peripheral neuropathy develop in it.

Weils syndrome is icteric form of leptospirosis which is characterized by hepatic dysfunction, renal insufficiency and multi-organ failure. Distinctive features in the form of jaundice, tender hepatomegaly appear on the 3rd to 6th day. Renal manifestations of V&ils syndrome consist primarily of proteinuria, hematuria, oliguria, Acute tubular necrosis and azotemia. Pulmonary symptoms include cough, haemoptysis, Broncho pneumonia, bilateral lung consolidation and ARDS. Myocarditis is another important complication.

Various cardiac arrhythmias (Atrial flutter, atrial fibrillation, Ventricular tachycardia) are known to occur as well as congestive heart failure. Aseptic meningitis occurs in small percentage of cases. Rhabdomyalysis, DIC, Thrombocytopenia and digital gangrene are there complications. Weils syndrome is serious form of leptospirosis and carries mortality ranging from 5- 15%.

Investigations

1. There is leucocytosis, thrombocytopenia, raised ESR and Mild anemia.

The organism can be grown from the blood and the CSF in first 10 days of illness and from urine in the third week. The organisms are identified by dark field examination or by culture in semisolid medium (Fletcher’s EMJH).

Serology

1. Microscopic agglutination test (MAT). It is the gold standard with either a four fold rise in titres or a single titre of> 1: 800.

2. ELISA 1gM and slide Agglutination test (SAl’). Measuring 1gM antibodies is useful in diagnosing current leptospirosis infection at an early stage.

Penicillin is the drug of choice (1,5 millions units I/V 6 hourly for 7 days). Other drugs which can be employed are Amoxycillin 500 mg 6 hrly for 7 days, Doxycycline 100 mg twice a day for 7 days. These therapeutic measures should be started at the earliest onset of symptoms.

If a patient has bleeding tendencies then whole blood or platelet transfusion be given. In cases with renal failure, haemo-dialysis may be required. When epidermic of leptospirosis is suspected in an area then all adults should be given doxycycline 200 mg orally every week.

Prognosis

It depends on the virulence of the organism and on the general condition of the patient, severity of the disease and presence of complications. Disease carries high mortality in elderly persons as well as those suffering from Weil’s syndrome.